When an attempt to send an electronic message, such as an email, from a sender to a recipient is unsuccessful, the electronic message is said to have “bounced.” The term “bounce,” as used herein, refers to the event of failing to successfully deliver an electronic message to a recipient. A recipient refers to any destination, such as an email address, identified in an electronic message that should receive the electronic message when the electronic message is delivered. A recipient that was sent an electronic message, but did not receive the electronic message because the electronic message bounced is referred to herein as a “bounced recipient.”
When a sender initiates delivery of an electronic message to a recipient, the sender's email server sends the electronic message to the recipient's email server over a network, e.g., the Internet, and thereafter the recipient's email server delivers the electronic message to the recipient. If the recipient's email server is not able to deliver the electronic message to the recipient, the recipient's email server may deliver a message rejection response (also known as a bounce message) to the sender's email server. A bounce message, as used herein, is a message that indicates that a particular recipient did not receive a particular electronic message delivered to the recipient. Depending on the configuration of the sender's mail server, a bounce message may also appear as a new message in the sender's inbox when an electronic message sent by the sender is bounced.
There are two kinds of bounces: a hard bounce and a soft bounce. A soft bounce occurs when the sender's mail server determines that it is likely that a bounce occurred because the recipient is temporarily unavailable. For example, a soft bounce may occur when the recipient's inbox is full and unable to accommodate additional electronic messages. A bounced messaged that experiences a soft bounce may be redelivered at another time.
On the other hand, a hard bounce occurs when the sender's mail server determines that (a) it is likely that a bounce occurred because the recipient is unavailable and (b) it is likely that the recipient will continue to remain unavailable. For example, a hard bounce may occur when the recipient's address is invalid. Typically, when a hard bounce is experienced by a particular electronic message, a message (“a hard bounce inform message”) is delivered to the sender of the bounced message by the sender's email server to inform the sender that the bounced message was not delivered to a bounced recipient identified in the bounced message.
A mail server typically follows the same approach in handling bounces for all electronic messages processed by the mail server. An administrator of a mail server may configure the operation of the mail server by establishing configuration information that describes how many times to attempt to redeliver an electronic message that was bounced (i.e., how many soft bounces should the mail server allow for each electronic message) before ceasing to redeliver the electronic message (i.e., determining that a hard bounce has occurred) and how long to wait between attempts to redeliver electronic messages. The mail server performs as configured for each electronic message processed by the mail server.
It is desirable to deliver electronic messages in a manner that increases the likelihood that electronic messages will be successfully delivered to their recipients. It is further desirable to promote the efficient delivery of electronic messages. The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.